Page 226 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Assessment of crude glycerol utilization for sustainable development of biorefineries 197

(Quispe et al., 2013). In 1846 Soberero invented nitroglycerin, a prominent explo-
sive raw material, which is manufactured from glycerol. Later, glycerol manufac-
tures were established in many nations in Europe, Japan, Russia, and the United
States. The boom of biodiesel industries results in increased production of glycerol.
Until 2003 the global ultimatum of glycerol was encountered by petrochemical and
soap industries. Between 2008 and 2012, global production of glycerol was
increased by 9.3% per year which slashed down the price of glycerol. It is estimated
that the growth of glycerol demand will be 3.5% per year in 2022. As we know,
glycerol is a multipurpose renewable raw material with two large emergence con-
sumer markets. The first one is an already existing market which demands high
purity and specifications for the use in food and pharmaceutical industries. The sec-
ond is the utilization of crude glycerol in the conversion of high-value products and
chemical intermediates. Thus market of crude glycerol is characterized by the high-
er volume of products with lower quality of the substrate. Asia-Pacific is acknowl-
edged as the principal consumer of glycerol with approximately 36% of the world’s
glycerol production (Kong et al., 2016).

9.3 Refining of crude glycerol

During biodiesel production along with catalyst, an excess amount of methanol is
used to convert more fat and oil into biodiesel (Sdrula, 2010). As a result the glyc-
erol phase has the tendencies to contain copious impurities, such as soap, methanol,
water, and salts, during the separation of biodiesel (Xu et al., 2012). Hence, crude
glycerol cannot be acquiescently used in food or pharmaceutical industries, and
also without proper treatment, it cannot be directly disposed to the environment
(Escapa et al., 2009; Gervasio et al., 2009). Alternatively, the crude glycerol from
biodiesel manufacturing plant can be used as a cheap substrate for production of
different valuable products. However, impurities present in crude glycerol restrict
its use in food and other industries. Therefore purification of crude glycerol is
required, in order to meet the requirements of prevailing and emergent uses (Yang
et al., 2012). A sequence or combination of treatment, such as distillation, acidifica-
tion, phase separation, adsorption with activated carbon, membrane filtration, and
ion exchange adsorption, could achieve the maximum purity glycerol of about
97.5%. Various stages of glycerol purification and its application were displayed in
Fig. 9.1.

9.3.1 Need for simple purification process
The simple purification process comprises a few processes based on the need and
quality of crude glycerol. Usually, the high yield of biodiesel is achieved in biodie-
sel production process in utilizing excess amount methanol transesterification pro-
cess. The unreacted excess methanol starts settled at crude glycerol phase as a
major impurity and which may inhibit the growth of the microorganism. The